Selective separation by a chromatographic process

ABSTRACT

A class of novel crystalline aluminosilicates generally identified as ZSM-5 type and having unique molecular sieving properties are utilized as selective sorbents in a chromatographic process. The effective portals in these zeolites are apparently elliptically shaped with effective major and minor axis of about 7.0 + OR - 0.7A and 5.0 + OR - 0.5A, respectively. This unique shape is utilized to provide &#39;&#39;&#39;&#39;keyhole&#39;&#39;&#39;&#39; molecular sieving action which is particularly useful for separating specific members of closely-related chemical compounds. A preferred embodiment is the selective separation of disubstituted hydrocarbons such as dialkyl aromatics. The process of this invention is particularly useful for separating C8 aromatic mixtures. A particularly preferred embodiment is the separation of p-xylene from a mixture of the same with o-xylene and/or m-xylene and/or ethylbenzene.

United States Patent 3,699,182 Cattanach 1 Oct l7, 1972 SELECTIVESEPARATION BY A CHROMATOGRAPHIC PROCESS Primary Examiner-Delbert E.Gantz Assistant Examiner-C. E. Spresser 72 l t h 1 men or J0 n CammachGhssboro N J Attorney-Oswald G. Hayes and Andrew L. [73] Assignee: MobilOil Corporation Gaboriault [22] Filed: Dec. 5, 1969 [57] ABSTRACT [2]]Appl' 882692 A class of novel crystalline aluminosilicates generallyidentified as ZSM-S type and having unique molecular 52 us. Cl ..260/674SA, 55/67, 208/310, sieving properties are utilized as selective sorbemsin a I v 260/67 MS chromatographic process. The effective portals in 51int. Cl ..C07c 7/12 these zeolites are pp y elliptically shaped with 53]Field f 2 674 SA, 7 MS, 666 SA, effective major and minor axis of about7.0 i 0.7A

2 0 77; 20 55 7 and 5.0 i 0.5A, respectively. This uniquev shape isutilized to provide keyhole molecular sieving action [56] ReferencesCited which is particularly useful for separating specific members ofclosely-related chemical compounds. A UNlTED STATES PATENTS preferredembodiment is the selective separation of disubstitutecl hydrocarbonssuch as dialkyl aromatics. g i The process of this invention isparticularly useful for pper y e a separating C aromatic mixtures. Aparticularly Asher preferred embodiment is the separation f p yl3,l14,782 12/1963 Fleck et al. ..260/674 from a mixture of the Same witho xylene and/or 3,133,126 5/1964 Fleck et al. ..260/674 Xyleneand/orethylbenzene 3,126,425 3/1964 Eberly et al. ..260/674 3,308,069 3/1967Wadlinger et al. ..252/455 11 Claims, No Drawings SELECTIVE SEPARATIONBY A CI-[ROMATOGRAPHIC PROCESS FIELD OF THE INVENTION of disubstitutedaromatic isomers from a mixture of the 10 same with other-isomers.

DESCRIPTION OF THE PRIOR ART -It has long been known that certain poroussubstances such as silica gel, activated char, and indeed zeolites, havecertain selective absorption characteristics useful in resolving ahydrocarbon mixture into its component parts. Thus, silica gel isselective in removing aromatic hydrocarbons from non-aromatichydrocarbons and activated chars are useful in separating olefins frommixtures with paraffins. Similarly, the molecular sieve properties ofzeolites can be utilized to selectively remove one molecular speciesfrom a mixture of the same with other species.

Although a wide variety of zeolitic materials, particularly crystallinealuminosilicates, have been successfully employed in various separationschemes, nevertheless, these prior an processes, in'general, fell intoone or two main categories. In one type a zeolite was employed having apore size sufficiently large to admit the vast majority of componentsnormally found in a process stream. These molecular sieves are referredto as large pore zeolites and they are generally stated to have a poresize of about 13A such as zeolite X, Y, and L. The other type ofcrystalline aluminosilicates are those having a pore size ofapproximately 5A which are utilized to separate small molecules such asn-paraffins to the substantial exclusion of other molecular species.

There are many separations, however, that the porous absorbents of theprior art are not capable of making efficiently. For instance, it wouldbe highly desirable to separate closely-boiling aromatics, particularlythe C aromatic mixture. 'Paraxylene, in particular, is required in avery high state of purity for the manufacture of terephthalic acid whichis an intermediate in the manufacture of synthetic fibers such asDacron. Normally it is separated from a product stream containingethylbenzene, m-xylene and o-xylene by costly superfractionation andmultistage refrigeration steps. This process involves high operatingcosts and has a limited yield.

Another proposed solution to this problem is set forth in US Pat. No.3,126,425. This patent discloses contacting a mixture of xylene isomerswith crystalline aluminosilicates such that the ortho and meta isomersare sorbed by said aluminosilicates and the para isomer is concentratedin the unabsorbed portion.

The above method is concerned with the concentration of the moresymmetrical disubstituted aromatic isomer, such as p-xylene, in theunadsorbed stream. It therefore apparently represents an extension ofthe normal relative partitioning of xylene isomers with high surfacearea solids to the more selective crystalline aluminosilicate surface.All of the isomers described in the above patent will be sorbed bycrystalline aluminosilicates having uniform pore opening of 10-13Angstrom units. The separations shown are therefore not dependent of themolecular sieving properties of the 13 Angstrom zeolite, but rather, onthe relative partitioning of the said isomers between theintracrystalline sorbed phase and the free liquid phase. This method istherefore severely limited and may as stated be restricted because ofeconomic considerations to processing only streams containing 50 percentor more para-xylene. The normal concentration of p-xylene in equilibriummixtures of xylene isomers obtained from commercial isomerization unitsis generally about 24 weight percent so that this method will notaccomplish the desired separation on feeds such as this.

' DESCRIPTION OF THE INVENTION It has now been discovered that uniqueselective separations can be achieved by utilizing a unique class ofcrystalline aluminosilicateswhich possess unique molecular sievingproperties in that they allow entry and egress to their internal 'porestructurev of not only normal paraffins but also of slightly branchedparaffins and yet have the ability to effectively exclude paraftinspossessing quartemary carbon atoms at short contact times. Thesezeolites also possess the ability of selectively sorbing simple,lightly-substituted monocyclic hydrocarbons from mixed hydrocarbonstreams containing highly-substituted monocyclic, polycyclic orheterocyclic or even simple polycyclic hydrocarbons. These zeolites alsopossess the unique property of selectively sorbing l,4-disubstitutedaromatic compounds in admixture with 1 ,2-, 1,3-, or more highlysubstituted aromatic hydrocarbons. Para-xylene, for example, can beselectively separated from orthoand meta-xylene by contacting saidmixture with this unique class of zeolites.

As has heretofore been stated, all the crystalline aluminosilicatematerials heretofore employed in prior art processes fell into one oftwo general types the small-pore zeolites having pore sizes of about SAand the large-pore zeolites having pore sizes of about 1 3A.

The small port aluminosilicates were generally stated to be shapeselective in that they allowed selective separation of normal aliphaticcompounds from a mixture of the same with isoaliphatic compounds andcyclic compounds. The second class of zeolites, i.e., those having apore size of 13A were generally stated to be non selective since all ofthe molecules normally found in a hydrocarbon feed stream are able toenter the internal pore structure. Separations by the large porezeolites are therefore generally restricted to relative partitioning ofsorbate molecules within the intracrystalline void volume according tothe relative polarity of the sorbate molecules.

The novel separation schemes of the invention are predicated upon usingzeolitic materials which allow selective separations to be achieveddepending on either the size, shape or polarity ,of the sorbatemolecules. This class of novel crystalline aluminosilicates cangenerally be stated to have intermediate shape-selective sorptionproperties. The unique nature of this novel class of zeolites ischaracterized by the presence of uniform pore openings which areapparently elliptical rather than circular in nature. The effective poreopenings of this unique class of zeolites have both a major and minoraxis, and it is for this reason that the unusual and novel molecularsieving ef- 0.9:O.2 Mg o I W203 I YO Z Z wherein M is a cation, n is thevalence of said cation, W is selected from the group consisting ofaluminum and gallium, Y is selected fromthe group consisting of siliconand germanium, and Z is from to 40. In a preferred synthesized form, thezeolite has a formula, in terms of mole ratios of oxides, as follows:

7 Mg o I A1203 I i Z H20 and M iS selected from the group consisting ofa mixture of alkali metal cations, especially sodium, and

tetraalkylammonium cations, the alkyl groups of which preferably contain2-5 carbon atoms.

In a preferred embodiment of ZSM-5, W is aluminum, Y is silicon and thesilica/alumina mole ratio is at least 10 and ranges up to about 60.

Members of the family of ZSM- zeolites possess a definite distinguishingcrystalline structure whose X- ray diffraction pattern shows thefollowing significant linesz' TABLE I lnterplanar Spacing d(A) RelativeIntensity These values as well as all other X-ray data were determinedby standard techniques. The radiation was the K-alpha doublet of copper,and a scintillation counter spectrometer with a strip chart pen recordedwas used. The peakheights', I, and the positions as a function of 2times theta, where theta is the Bragg angle, were read from thespectrometer chart. From these, the'relative gest line or peak, and d(obs.), the interplanar spacing in A, corresponding to the recordedlines, were calculated. In Table I the relative intensities are given interms of the symbols S strong, M medium, MS

medium strong, MW =medium weak and VS very strong. It should beunderstood that this X-ray difi'raction pattern is characteristic of allthe species of ZSM-5 compositions. Ion exchange of the sodium ion withother cations reveals substantially the same pattern with some minorshifts in interplanar spacing and variation in relative intensity. Otherminor variations can occur depending on the silicon to aluminum ratio ofthe particular sample, as well as if it had been subjected to thermaltreatment. Various cation exchanged intensities, 100 U], where I is theintensity of the stronforms of ZSM-S have been prepared. X-ray powderdiffraction patterns of several of these forms are set forth below. TheSZM-S forms set forth below are all aluminosilicates.

TABLE 2 X-Ray Diffraction ZSM-5 Powder in Cation Exchanged Forms dSpacings Observed As Made HCl NaCl CaCl, RECl; AgNO,

Zeolite ZSM-S can be suitably prepared by preparing a 8 solutioncontaining tetrapropyl ammonium hydroxide, sodium oxide, an oxide ofaluminum or gallium, an oxide of silica or germanium, and water andhaving a composition, in terms of mole ratios of oxides, falling withinthe following ranges:

wherein R is propyl, W is aluminum or gallium and Y is silicon orgermanium maintaining the mixture until crystals of the zeolite areformed. Thereafter, the crystals are separated from the liquid andrecovered. Typical reaction conditions consist of heating the foregoingreaction mixture to a temperature of from about 90to 200C for a periodof time of from about 6 hours to 60 days. A more preferred temperaturerange is from about 100to 175C with the amount of time at a temperaturein such range being from about 12 hours to 8 days.

The digestion of the gel particles is carried out until crystals from.Thesolid product is separated from the reaction medium, as by coolingthe whole to room temperature, filtering, and water washing.

The foregoing product is dried, e.g., at 230F, for from about 8 to 24hours. Of course, milder conditions may be employed if desired, e.g.,room temperature under vacuum.

ZSM-S is preferably formed as an alurninosilicate. The composition canbe prepared utilizing materials which supply the appropriate oxide. Suchcompositions include for an aluminosilicate, sodium aluminate, alumina,sodium silicate, silica hydrosol, silica gel, silicic acid, sodiumhydroxide and tetraproplammonium hydroxide. It will be understood thateach oxide component utilized in the reaction mixture for preparing amember of the ZSM-5 family can be supplied by one or more initialreactants and they can be mixed together in any order. For example,sodium oxide can be supplied by an aqueous solution of sodium hydroxide,or by an aqueous solution of sodium silicate; tetrapropylammonium cationcan be supplied by the bromide salt. The reaction mixture can beprepared either batchwise or continuously. Crystal size andcrystallization time of the ZSM-S composition will vary with the natureof the reaction mixture employed. ZSM-S is disclosed and claimed in Ser.No. 865,472, filed Oct. 10, 1969.

Another operable zeolite falling within the above class is zeolite ZSM-Swhich is described and claimed in Ser. No. 865,418, filed Oct. 10, 1969.865,472,

ZSM-8 can also be identified, in terms of moleratios of oxides, asfollows:

Mgj o I A1203 I Z Z H2O wherein M is at least one cation, n is thevalence thereof and z is from 0 to 40. In a preferred synthesized form,the zeolite has'a formula, in terms of mole ratios of oxides, asfollows:

0.91:0.2 M O A1 0 10-60 SiO 2 H 0 and M is selected from the groupconsisting of a mixture of alkali metal cations, especially sodium, andtetraethylarnmonium cations.

ZSM-8 possesses a definite distinguishing crystalline structure havingthe following X-ray diffraction pattern:

TABLE4 dA" 1/1 1/1, dA

Zeolite ZSM-8 can be suitably prepared by reacting a solution containingeither tetraethylarnmonium hydroxide or tetraethylammonium bromidetogether with sodium oxide, aluminum oxide, and an oxide of silica andwater.

The relative operable proportions of the various ingredients have notbeen fully determined and it is to be immediately understood that notany and all proportions: of reactants will operate to produce thedesired zeolite. In fact, completely different zeolites can be preparedutilizing the same starting materials depending upon their relativeconcentration and reaction conditions as is set forth in U.S.Pat. No.3,308,069. In general, however, it has been found that whentetraethylammonium hydroxide is employed, ZSM-8 can be prepared fromsaid hydroxide, sodium oxide, aluminum oxide, silica and water byreacting said materials in such proportions that the forming solutionhas a composition in terms of mole ratios of oxides falling within thefollowing range 1 SiO /Al O from about to about 200 Nao/tetraethylammonium hydroxide from about Tetraethylammoniumhydroxide/Si0 from about 0.08 to 1.0 H O/tetra'ethylammonium hydroxidefrom about 80 to about 200 Thereafter, the crystals are separated fromthe liquid and recovered. Typical reaction conditions consist of heatingthe foregoing reaction mixture to a temperature of from about 100 to175C for a period of time of from about 6 hours to 60 days. A morepreferred temperature range is from about 150 to 175C with the amount oftime at a temperature in such range being from about 12 hoursto 8 days.

The digestion of the gel particles is carried out until crystals form.The solid product is separated from the reaction medium, as by coolingthe whole to room temperature, filtering, and water washing.

The foregoing product is dried, e.g., at 230F, for from about 8 to 24hours. 0f course, milder conditions may be employed if desired, e.g.,room temperature under vacuum. v

ZSM-.-8 is prepared utilizing materials which supply the appropriateoxide. Such compositions include sodium aluminate, alumina, sodiumsilicate, silica hydrosol, silica gel, silicic acid, sodium hydroxideand tetraethylammonium hydroxide. It will be understood that each oxidecomponent utilized in thereaction mixture can be supplied by one or moreinitial reactants and they can be mixed together in any order. Forexample, sodium oxide can be supplied by an aqueous solution of sodiumhydroxide, or by an aqueous solution of sodium silicate,tetraethylammonium cation can be supplied by the bromide Salt. Thereaction mixture can be prepared either batchwise or continuously.

The zeolites used in the instant invention can have the original cationsassociated therewith replaced by a wide variety of other cationsaccording to techniques well known in the art. Typical replacing cationswould include hydrogen, ammonium and metal cations including mixtures ofthe same.

Typical ion exchange techniques would be to contact the particularzeolite with a salt of the desired replacing cation or cations. Althougha wide variety of salts can be employed, particular preference is givento chlorides, nitrates and sulfates.

Representative ion exchange techniques are disclosed in a wide varietyof patents including US. Pat. Nos. 3,140,249; 3,140,251; and 3,140,253.

Following contact with the salt solution. of the desired replacingcation, the zeolites are then preferably washed with water and dried ata temperatureranging from 150 to about 600F and thereafter calcined inair or other inert gas at temperatures ranging from about 500 to 1,500Ffor periods of time ranging from 1 to 48 hours or more.

Prior to use, the zeolites should be dehydrated-at least partially. Thiscan be done by heating to a temperature in the range of 200 to 600C inan atmosphere, such as air, nitrogen, etc. and at atmospheric orsubatmospheric pressures for between 1 and 48 hours. Dehydration canalso be performed at lower temperatures merely by using a vacuum, but alonger dimethyl-butane,

time is required to obtain a 'sufi'lcient amount of dehydration. v I

The novel process, of this invention is applicable. to the separation ofspecific compounds and classes of compounds from mixtures of the samewith other compounds. In order to aid in pointing out the separationswhich can be accomplished by the instant process Table 5 is presented.This table lists in column A those compounds or classes of compoundswhich can be separated from mixtures of the same with other compounds orclasses of compounds listed in column B. For convenience, columns A andB are further sub-divided into three parts, i.e., 1, 2 and 3 to depictthose separations which are most usually encountered.

TABLE 5 B 1. Compounds having a quaternary carbon atom 2.Polysubstituted aromatics and naphthenes; and polycyclic aromatics andnaphthenes A 1. Alkyl substituted nonquartcmary carbon containingparalfins or olefins.

3. Other substituted biphenyls Thus, from the above table it can be seenthat the materials listed under A1 are usually separated from mixturesof the same with materials listed under B1. It is to be understood,however, that any material listed under A can be separated from anymaterial listed under B. In some cases it is even possible to make aseparation between two or more compounds listed under A, althoughseparation of this type are not usually made.

Examples of compounds of the A1 type include 2- methylbutane,2-methylpentane, 3-methylpentane, 2,3-

2-methylhexane, 3-methylhexane, 2,3-dimethylpentane,3,4-dimethylpentane, 2-methylheptane, 3-methylheptane, 4-methylheptane,2,4- dimethylhexane, 2,3-dimethylhexane, 2,5-dimethylhexane,3,4-dimethylhexane, 2,3,4-trimethylpentane, S-methylhexene l4-methylhexenel 3,4-dimethyl hexenel, 4-methylhexene-2. Examples ofcompounds of the B1 type include 2,2-dimethylpropane, 2,2-dimethylbutane, 2,2-dimethylpentane, 3,3-dimethylpentane,2,2,3-trimethylbutane, 2,2-dimethylhexane,

3 ,3-dimethylhexane, 2,2,3-trimethylpentane, 2,2,4- tn'methyl-pentane,2,3,3-trimethylpentane, 2,2,3,3- tetramethylbutane, 3,3-dimethylhexene-1 4,4- dimethylhexenel 3 ,3 ,4-trimethylhexene-l 3 ,3-

dimethylbutane-l Examples of compounds of the A 2 type include benzene,cyclohexane, toluene, ethyl benzene, methyl cyclohexane, propyl benzenepara-xylene, 1,4-diethyl benzene, l-ethyl-4-methyl benzene, 1,4-dimethylcyclohexane, methyl cyclopentane, l-methyl-4-ethyl cyclohexane,l-propyl-4-ethyl benzene, l-hexyl-4-ethyl benzene.

Examples of compounds of the B2 type include oxylene, m-xylene,1,2-diethyl benzene, 1,3-diethyl benzene, l-propyl-3-hexyl benzene,l-ethyl-2-propyl, l,3,5-trimethyl benzene, 1,2,4-triethyl benzene,1,3,5- triethyl cyclohexane, 1,1,4-tripropyl cyclopentane, deca lin,anthracene, phenanthrene.

Examples of compounds of the A3type include biphenyl, 4-methyl biphenyl,4-ethyl biphenyl, 4-hexyl biphenyl, 4,4-dimethylbiphenyl,4-methyl-4-ethyl biphenyl.

Examples of compounds of the B3 type include 3,3- dimethyl biphenyl,5-ethyl-3-hexyl biphenyl, 2,3,3- trimethyl biphenyl, 2,2-diethylbiphenyl.

As has heretofore been stated compounds of the Al type are usuallyseparated from a mixture of the same with at least one compound of theB1 type. In like manner compounds of A2 are usually separated from amixture of the same with B2 and A3 from B3. In this connection, apreferred utilization of the novel chromatographic process of thisinvention resides in the resolution of a mixture of isomers since, ingeneral, this type of separation is difficult to accomplish byconventional techniques. Thus, for example, 2,4-dimethyl pentane can beseparated from 3,3-dimethyl pentane. The most preferred embodiment ofthis invention resides in the separation of a mixture of C aromaticsparticularly the separation of para-xylene from a mixture of the samewith ortho xylene and/or meta-xylene and/or ethyl benzene.

As has been stated, the separation process of this invention is achromatographic one. This is intended to describe a process whereinseparation is based on selective adsorption of at least one component ofa mixture by a solid. The solid is the ZSM-S type zeolite previouslydescribed.

The novel chromatographic separation process of this invention iscarried out merely by contacting a hydrocarbon mixture, above-described,existing either as a gas, liquid or mixed phase with a crystallinezeolite of the ZSM-S type such that the desired component isconcentrated in either the absorbed or non-absorbed phase. A suitablefluid carrier can be employed if such is desired. Typical carriersinclude polar and non polar compounds such as nitrogen, air, water,hydrocarbons, helium, etc. The process can be carried out in either abatch or a continuous operation. The sorbed material can be subsequentlyrecovered by conventional desorbing techniques such as thermalstripping, stripping with an inert gas, e.g., nitrogen, helium, etc. orevacuation of elutriation with a suitable polar or non-polar strippingagent, e.g., water, n-hexane, etc.

The temperature at which the separation is carried out is important. Itcan be stated that the novel process of this invention can be carriedout at temperatures ranging from about S0 to about 400C. It is notedthat higher temperatures can be employed but because of possibility ofcatalytic conversion, 400C appears to be a suitable upper limit. A morepreferred temperature range appears to be between about 25 to 300C. It

is noted that the above temperatures might vary slightly depending uponthe particular cationic form of the crystalline aluminosilicate employedbut, in general, they represent operable parameters for carrying out thenovel process of this invention.

In another embodiment of this invention, it is desired to incorporatethe ZSM-S typezeolite with another material resistant to thetemperatures and other condimetal oxides.

Naturally occurring clays which can be composited with the ZSM-S typezeolite include the montmorillonite and kaolin family, which familiesinclude the sub-bentonites, and the kaolins commonly known as DixieMcNamee-Georgia and Florida clays or others in which the main mineralconstituent is halloysite, kaolinite, dickite, nacrite, or anauxite.Such clays can be used in the raw state as originally mined or initiallysubjected to calcination, acid treatment or chemical modification.

In addition to the foregoing materials, the ZSM-S type zeolite can becomposited with a porous matrix material such as silica-alumina,silica-magnesia, silicazirconia, silica-thoria', silica-beryllia,silica-titania as well as ternary compositions such assilica-aluminathoria, silica-alumina-zirconia, silica-alumina-magnesiaand silica-magnesia-zirconia. The matrix can be in the fonn of a cogel.The relative proportions of finely divided crystalline aluminosilicateZSM-S and inorganic oxide gel matrix vary widely with the crystallinealuminosilicate content ranging from about 1 to about 99 percent byweight and more usually, particularly when the composite is prepared inthe form of beads in the range of about 40 to about 90 percent by weightof the composite.

Another embodiment of this invention resides in sub- 5 5 jecting thezeolite ZSM-S type to a mild steam treatfore, after or in place of thecalcination treatment.

A similar treatment may be accomplished at lower temperatures andelevated pressures, e.g., 350-700F at 10 to about 200 atmospheres.

The following examples will illustrate the best mode contemplated forcarrying out the present invention.

EXAMPLES l-4 Typical preparations of ZSM-5 type zeolites are shown inthese examples. Examples 1-3. show the preparation of the hydrogen formZSM-S and they involve the use of tetrapropyl-ammonium hydroxide (T-PAOH) or bromide (TPABr). Example 4 shows a typical preparation of thehydrogen form ZSM-8 using tetraethyl. ammonium hydroxide (TEAOH).Reaction conditions and results are shown in Table 6.

TABLE 6 281 g Sorbead Reaction 30 g NaAlO vFines 0.56 lb. 13 g NaAlO,Compo- 720 g Ludox 3.3 lb NaAlO 300 g sition 1025 g of TPABr I 44.7 lb40% TEAOH 2.2N TPAOH Solution Q-Brand 300 g H O 5.6 lb 1000 g LudoxTPABr 16.7 lb NaCl 4.5 lb H=SO 132.0 lb H O Reaction temp (C) 150 100100 193 time (hr) 168 168 327 144 Washed dried at 230F, calcined 16 hrsat 1000F Base Exchange NH CI Solution Conc.

(Wt 2S 5 25 25 temp. (C) 90 25 90 l 90 contacts X3 X4 X3 X3 pelletedcalcined (hr) 16 1O 16 16 (F) 1000 1000 1000 1000 steamed 1 (hr) 14 2414 14 (F) 1290 1200 1290 1290 (psia) 15 30 l5 15 Chemical Composition(21 3-) Na 0.08 0.23 0.02 .5 A1 4.7 2.2 3.0 3.0 Sio 969 95.3 94.8 95.9X-ray type ZSM- ZSM-5 ZSM-S ZSM-8 EXAMPLE 5 containing 70 wt. m-xyleneand 30 wt. p-xylene was pumped to the top of the column at a pumpingspeed of 20 ml/hr and a helium flow of 25 ml/hr was maintained throughthe column. Fractions were eluted from the column using a helium flowand water was a stripping agent. The eluted fractions were trapped andisolated in cooled (-196C) glass traps.

Analysis of the initial fraction showed that it was substantially purem-xylene.

Analysis of the fraction obtained after the addition of 9.7 grams ofwater at a flow rate of 20 ml/hr showed that it was 98 percent purep-xylene.

EXAMPLES 6-8 These examples will illustrate selective separation ofparaxylene from a solution comprising 24 wt. i pxylene, 59 wt. m-xyleneand 17 wt. o-xylene.

In each of Examples 6-8, 50 grams of a zeolite of the ZSM-5 type wascontacted with the solution of xylene isomers for 1 hour at atemperature of 25C. In Example 6 the zeolite employed was then preparedby the general procedure of Example 1. in Example 7, the zeoliteemployed was that prepared by the general procedure of Example 2, andinExample 8 the zeolite employed was that prepared by the generalprocedure of Example 4. After contact for one hour, the solution wasfiltered and the unabsorbed fraction was analyzed.

than 99 percent. A summary of 7 these experiments in- V eluding detailedanalysis is shown in Table 7.

TABLE 7 Example 6 7 8 Sorbent Type HZSM-S HZSM-S HZSM-B (TPAOH) (TPABr)(TEAOH) Solution Composition (Wt p-xylen'e 24 24 24 m-xylene 59 59 59o-xylene l7 17 17 Contact Time (hrs) 1 l 1 Temp. (C) 25 25 25 Separation15 min filtration Unadsorbed Fraction Wt of filtrate (g) 68 67 66Composition (Wt p-xylene l 7 l 6 l 7 m-xylene 65 66 65 o-xylene 18 y l8l8 Sorbed Fraction Wt of Filter Cake (g) 74 73 69 Wash 100 g ofMesitylene Extraction Procedure 20 hrs Soxhelt extraction (1.5 liter ofnC H at 50C) Wt of Extract (g) 230 221 193 Composition (Wt normal hexane94 95 xylene isomers l l l mesitylene 4 5 4 Wt of Xylene Fraction (g)1.8 1.8 1.7 Composition (Wt p-xylene 99 99 99 m-xylene o-xylene Grams ofp-xylene Recovered/ 100 g Solid 3.6 3.6 3.4

EXAMPLES 9-16 A 50-50 mixture of various hydrocarbons were passed over a5 X inch column containing 3.8 grams of 30/60 mesh HZSM-8 prepared bythe procedure of Example 4. The procedure involved injecting 50microliters of the various 50/50 mixtures into the column into which wasflowing a helium gas stream at a flow rate of 100 ml/min. The varioushydrocarbon samples were passed through a preheater zone at 225C at thecolumn inlet. Elution of the hydrocarbons in the exit helium stream wasmonitored. The results obtained are shown in Table 8. In each casepurities of greater than 90 percent were obtained.

TABLE8 Elution Temp. Time Component (C) Components mixturesec to sec 90%purity) 9 200 2,2-dimethylbutane:

2-methylpentane /30 2,2-dimethylbutane 1 l 80/ 300 Z-methylpentane 10200 lsooctane:

3-methylpentane 0/ l0 lsooctane 210/360 3-methylpentane 11 200lsooctane: I 2,5-dimethylhexane 0/ l0 Osooctane 35/85 2,5-dimethylhexane12 200 Decalin:

cyclohexane 0/6 Decalin 70/220 Cyclohexane 1,2dimethyl- 13 225cyclohexane :methylcyclohexane .0/6 l,2-dimethylcyclohexane 80/210Methylcyclohexane 14 225 O-diethylbenzene:

p-diethylbenzene 0/10 Q -di ethylbenzene I 1 20/200 p-diethyl Benzene 15225 m-xylene: p-xylene 0/ 15 rn-xylene 60/1 10 -sryreit? 16 2252-ethyltoluene:

4-ethyltoluene 0/ l0 2-ethyltoluene 75/160 4-ethyltoluene EXAMPLES 17-24 The procedure of Examples 5-16 was repeated with the exception thatthe zeolite employed was HZSM-S. This zeolite was prepared in accordancewith the procedure of Example 1. The results of these examples as wellas the specific hydrocarbon mixtures employed areshown in Table 9.

TABLE9 Elution ex. Temp. Components in Mixture Time Component (C)(50/50) sec to see 90% purity) I7 200 2,2-dimethylbutane:

Z-methylpentane 0/30 2,2-dimethylbutane 180/300 Z-methylpentane 18 250lsooctane:

B-methylpentane 0/ l0 lsooctane 210/360 3-methylpentane 19 200lsooctane:

2,5-dimethylhexane 0/ 10 Isooctane 35/80 2,5-dimethylhexane 20 250Decalin:

cyclohexane 0/5 Decalin 70/220 Cyclchexane 1,2-dimethyl- 1 21 250cyclohexane :methylcyclohexane 0/5 l,2-dimethylcyclo hexane 80/210Methylcyclohexane 22 200 O-diethylbenzene:

p-diethylbenzene 0/10 O-diethylbenzene 1 15/200 p-diethylbenzene 23 200m-xylene:

p-xylene O/ l 5 m-xylene 60/100 p-xylene 24 200 Z-ethyltoluene:

4-ethyltoluene 0/ l0 2-ethyltoluene 70/ l 60 4-ethyltoluene LII EXAMPLE25-28 Examples 25-28 are directed towards the separation of variousxylene isomers both with and without ethylbenzene over a zeolite of theZSM-S type. In each of these examples about 4 grams of the zeoliteprepared in accordance with the procedure of Example 1 was sized 30/60mesh and then packed into a 5 inch diameter sorption column. The zeolitecolumn was then activated and flowing helium at a flow rate of 100ml/min. at 300C and thereafter cooled to 175C. A 100 microliter sampleof the C aromatic mixture was then injected into the helium streamimmediately ahead of the sorbent column through a preheater zone 225C.Elution of the various components in the exit helium stream weremonitered and specific fractions were isolated from said exit heliumstream in sample vials which were cooled to C. The fractions were thenremoved andanalyzed. The specific operating conditions as well as theresults of these experiments are shown in Table 10. 1 Y 1 TABLE 10Example 25 26 27 28 Starting Composition Ethylbenzene 8 12 P-Xylene 2423 22 M-xylene 76 59 5l 66 O-xylene 17 18 Fraction trapped betweenElution Times'of I I84 7 I87 157 secs to secs 347 245 247 247 Weight ofTrapped Sample (mg) 8 7 7 11 Final Composition (Wt Ethylbenzene P-xylene98 98 98 98 M-xylene 2 2 2 2 O-xylene From the above table, it can beseen that the novel procedure of this invention resulted in theseparation of substantially pure p-xylene from various isomeric mixturesthereof and in both the presence and absence of ethyl benzene.

EXAMPLES 29-3 2 The procedure of Examples 25-28 was repeated with theexception that separation process was carried out at C instead of C.Additional operating conditions, as well as the results of theseexperiments are shown in Table 1 1 EXAMPLES 33-38 The procedure ofExamples 25-28 was repeated with the exception that a 200 microlitersample was employed in Examples 33-36 inclusive, and the separation wascarried out at 175C. For example 37-38, the temperature employed was200C and the sample size employed was 100 microliters.

Other specific operating conditions, as well as the results obtained areshown in Table 12.

,ml/min. was employed in accordance with the trapped in vials at 80C andanalyzed. More detailed 7. .5. 6 Examples 39-42 44 20 so 10o l80 330 946 The procedure of Examples 29-32 was repeated with 45 g 8g g theexception that a ZSM-8 zeolite prepared by the 360 720 Q 5 procedure ofExample 41 was employed. 5 46 100 0 60 100 Other operational details, aswell as the results are 108 288 98 2 330 780 97 3 shown in Table 13. 47150 0 40 f 0 78 240 3 95 2 EXAMPLES 43-47 330 780 97 3 In these examplesa mixture comprising 14 Wt. 10 ethyl benzene, wt. p-xylene, and 61 wt.mxylene was charged to 3.6 grams of a /60 mesh EXAMPLES 48--53v HZSM-Szeolite prepared in accordance with the procedure of Example 1. Thezeolite was contained in a 5 X inch ,columm and the temperatureseparation was carried out at 175C. Helium at a flow rate of 100 Theprocedure of Examples 43-47 was repeated with l 5 the exception that thezeolite employed was one of the ZSM-8 type prepared in accordance withthe procedure of Example 4. The composition which was charged consistedof 14 wt. ethylbenzene, 24 wt. paraxylene and 62 wt. metaxylene. Theresults of the separations, as well as more detailed operationconditions are shown in Table 15.

procedure of Examples 25-28 and samples were operating conditions aswell as the results of the separation are shown in Table 14.

TABLE 11 Starting composition (wt. percent) Fraction trapped Weight ofFinal composition (wt. percent) between elution trapped Ethyl timeoi(secs. sample Ethylbenzene p-Xylene m-Xylene o-Xylene to secs.) (mg.)benzene p-Xylene m-Xylene o-Xylene Example: I

24 76 "{620to1,040 I so 24 s9 17 {gfffg,

0 to 180 31 8 23 51 18 to 960 1,180 m 2,1 0 to 180 32 12 22 66 570t09001,600 to 2,100

TABLE 12 Starting composition (wt. percent) Fraction trap ed Weight ofFinal composition (wt. percent) between elu on trapped Ethyltimeof-(secs. sample Ethylbenzene p-Xylene m-Xylene o-Xylene to sees.) (mg.)benzene p-Xylene m-Xylene o-Xylene Example:

33 24 76 1441:0348 38 99 24 59 17 162 to 385-. 31 99 23 61 18 119 to229.- 26 99 22 66 109 to 2 28 98 23 51 18 65 to 116 16 97 23 51 18 74 to112 97 TABLE 13 Starting composition (wt. percent) Fraction trappedWeight of Final composition (wt. percent) between elution trappedEthyltime 0f-(5ecs. sample Ethylbenzene p-Xylcne m-Xylene o-Xylene tosecs.) (mg.) benzene p-Xylene m-Xylene o-Xylene Example TABLE 14EXAMPLES 54-61 Fraction These examples will illustrate the separation ofm- S pl xylene from p-xylene.

am e Size Elmo Finalcomposmon w In each 0t these examples a solutioncontaining 24 Ex. (IL) Times of Ethylp-xylene m-xylene parts by weightand 76 parts by weight of m-xylene m heme were charged to 4.3 grams of a30/60 mesh crystalline aluminosilicate prepared in accordance with the rlitews n in dina 43 l0 0 60 p ocedure of Example 2 The zeo a co ta e 390450 93 7 5 X inch column and the temperature at which the separation wascarried out was 150. The C aromatic sample was injected and vaporized at225C and the carrier was a helium stream at a flow rate of 100 ml/min.The eluted sample was trapped in glass vials at '-80C from the exithelium stream. More detailed operating conditions, as well as theresults of these experiments are shown in Table 16.

EXAMPLES 62-65 The procedure of Examples 54-61 was repeated with theexception that the temperature at which the separation was carried outwas 200C instead of 150C. Specific operating conditions, as well as theresults thereof are shown in Table 17.

TABLE 15 Fraction Trapped Sample between Size Elution Final Composition(Wt Ex. (#1.) Times of Ethylp-xylene m-xylene sec to sec benzene.

48 10 6O 100 168 360 100 49 20 0 30 l00 162 318 84 16 O 50 O 30 100 144288 100 378 660 100 51 100 0 30 100 120 288 100 TABLE 16 Separation ofm-xylene (30%) and p-xylene (70%) Sample Size Fraction Trapped Final Ex.(4 Between Elution Composition (Wt Times of p-xylene m-xylene secs tosecs 54 2S 0 20 100 450 960 l00 55 50 0 -30 100 450 960 I00 56 100 0 30100 360 960 100 57 200 0 30 100 360 960 100 58 300 0 30 100 180 960 10059 400 0 30 100 72 900 l00 60 500 0 30 100 900 61 600 0 3O 100 TABLE 17Sample Fraction Trapped Final Size Between Elution Composition (Wt Ex.(u) Time of p-xylene m-xylene Secs to Secs What isclaimed is:

1. A process for the selective separation of biphenyls selected from thegroup consisting of unsubstituted biphenyl non-quaternary carbon atomcontaining para substituted biphenyl and non-quatemary carbon atomcontaining para, para disubstituted biphenyl from a mixture of the samewith at least one other substituted biphenyl which comprises contactingsaid mixture with a crystalline zeolitic material for a period of timesufficient to selectively sorb at least one biphenyl, said zeoliticmaterial having the X-ray diffraction pattern as set forth in Table I ofthe specification and a composition, in terms of mole ratios of oxides,as follows:

0.9 $0.2 M ,,,O W 0 1 5-100 YO lZ H O wherein M is a cation, n is thevalence of said cation, W is selected from the group consisting ofaluminum and gallium, Y is selected from the group consisting of siliconand germanium, and z is from 0 to 40.

2. A process for the selective separation of para disubstituted aromaticisomers from a mixture of the same with at least one other isomericdisubstituted aromatic compound which comprises contacting said mixturewith a crystalline zeolitic material for a period of time tosufficiently sorb said para isomers, sad zeolitic material having theX-ray diffraction pattern as set forth in Table I of the specificationand a composition, in terms of mole ratios of oxides, as follows:

0.9 $0.2 M ,,,0 W 0 5-100 YO 'Z 2 H 0 wherein M is a cation, n is thevalence of said cation, W is selected from the group consisting ofaluminum and gallium, Y is selected from the group consisting of siliconand germanium, and z is from 0 to 40.

3. The process of claim 2 wherein the zeolite is ZSM-S and has an X-raydiffraction pattern selected from at least one of the cationic forms setforth in Table 2 of the specification. i

4. The process of claim 2 wherein the zeolite is ZSM-8 and has an X-raydiffraction pattern as set forth in Table 4 of the specification.

5. A process for the selective separation of paraxylene from a mixturewith at least one other isomeric Mzlno I W203 I I Z 20 wherein M is acation, n is the valence of said cation, W is selected from the groupconsisting of aluminum and gallium, Y is selected from the groupconsisting of silicon and germanium, and z is from 0 to 40.

6. The process of claim 5 wherein the temperature ran e is from 25 to300C.

. A process for the selective separation of paraxylene from a mixture ofthe same with at least one other isomeric xylene which comprisescontacting the same with a ZSM-S type zeolite to preferentially sorbparaxylene thereafter recovering said paraxylene from the internal porestructure of said zeolite, said zeolite having the X-ray diffractionpattern as set forth in Table l 'of the specification and a composition,in terms of mole ratios of oxides, as follows:

wherein M'is a cation, n is the valence of said cation, W

is selected from'the group consisting of aluminum andgallium, Y isselected from the group consisting of silicon and germanium, and z isfrom to 40.

8. A process for the selective separation of paraxylene from a mixtureof the same with at least one other isomeric xylene whichcomprisescontacting the same with ZSM-S at a temperature of 25-300C topreferentially sorb paraxylene thereafter recovering said paraxylenefrom the internal pore structure of said zeolite, said ZSM-S having theX-ray diffraction pattern selected from at least one of the. cationicforms set forth in Table 2 of the specification and a composition, interms of mole ratios of oxides, a follows:

0.9:02 M O A1 0 5-100 SiO 1 2 H 0 and M is selected from the groupconsisting of a mix- .tetraalkylammonium cation s, the alkyl groups ofwhich preferably contain 2-5 carbon atoms.

9. A process for the selective separation of paraxylene, from a mixtureof the same with at least one other isomeric xylene which comprisescontacting the same with ZSM8 to preferentially sorb paraxylenethereafter recovering said paraxylene from the internal pore structureof said zeolite, said ZSM8 having the X-ray diffractionpattern as setforth in Table 4 of the 10 specification and a composition, in terms ofmole ratios tureof alkali metal cations, especially sodium, and

of oxides, as follows:

0.9;+.2.M2,,,O 1 A1203 5-100 sioz z 11 0 the zsM-s is in 55? UNITEDSTATES PATENT OFFICE CERTIFIQATE OF CORRECTEUN Patent No'. 3, 99,1 2 weeOctober 17, 1972 Inventor-( OHN CATTANACH It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

F- Column 1, l1ne53, Table 2, under heading HCl, "2.75"

should be "2.7 1", Column 5, line 21, Table 2., under heading HCl,"1.4?" should be -l.57-; Column 5, line 39, Table 3, under headingParticularly Preferred, lo-5o" should be --lO- LO'; Column 6, line 15,delete "865 172."; Column 6, line 43, Table 1, under heading I/I firstoccurrence, L" should be --5-- Column 15, line 6, "results are should be--results obtained are-; Column 17, line 32, Table 15, under heading EX."52" should be -53--5 Column 18, line 25, "sad" should be said-;

Signed and sealed this 27th day of March 1973.

(SEAL) Attest: I

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. A process for the selective separation of para disubstituted aromaticisomers from a mixture of the same with at least one other isomericdisubstituted aromatic compound which comprises contacting said mixturewith a crystalline zeolitic material for a period of time tosufficiently sorb said para isomers, sad zeolitic material having theX-ray diffraction pattern as set forth in Table I of the specificationand a composition, in terms of mole ratios of oxides, as follows: 0.9 +or - 0.2 M2/n0 : W203 : 5-100 YO2 : z H2o wherein M is a cation, n isthe valence of said cation, W is selected from the group consisting ofaluminum and gallium, Y is selected from the group consisting of siliconand germanium, and z is from 0 to
 40. 3. The process of claim 2 whereinthe zeolite is ZSM-5 and has an X-ray diffraction pattern selected fromat least one of the cationic forms set forth in Table 2 of thespecification.
 4. The process of claim 2 wherein the zeolite is ZSM-8and has an X-ray diffraction pattern as set forth in Table 4 of thespecification.
 5. A process for the selective separation of paraxylenefrom a mixture with at least one other isomeric xylene which comprisespassing said mixture at a temperature of -50* to about 400*C with acrystalline aluminosilicate for a period of time to selectively sorbsaid paraxylene within the internal pore structure of said zeolite, saidaluminosilicate having the X-ray diffraction pattern as set forth inTable I of the specification and a composition, in terms of mole ratiosof oxides, as follows: 0.9 + or - 0.2 M2/nO : W2O3 : 5-100 YO2 : z H2Owherein M is a cation, n is the valence of said cation, W is selectedfrom the group consisting of aluminum and gallium, Y is selected fromthe group consisting of silicon and germanium, and z is from 0 to
 40. 6.The process of claim 5 wherein the temperature range is from 25* to300*C.
 7. A process for the selective separation of paraxylene from amixture of the same with at least one other isomeric xylene whichcomprises contacting the same with a ZSM-5 type zeolite topreferentially sorb paraxylene thereafter recovering said paraxylenefrom the internal pore structure of said zeolite, said zeolite havingthe X-ray diffraction pattern as set forth in Table 1 of thespecification and a composition, in terms of mole ratios of oxides, asfollows: 0.9 + or - 0.2 M2/nO : W2O3 : 5-100 YO2 : z H2O wherein M is acation, n is the valence of said cation, W is selected from the groupconsisting of aluminum and gallium, Y is selected from the groupconsisting of silicon and germanium, and z is from 0 to
 40. 8. A processfor the selective separation of paraxylene from a mixture of the samewith at least one other isomeric xylene which comprises contacting thesame with ZSM-5 at a temperature of 25*-300*C to preferentially sorbparaxylene thereafter recovering said paraxylene from the internal porestructure of said zeolite, said ZSM-5 having the X-ray diffractionpattern selected from at least one of the cationic forms set forth inTable 2 of the specification and a composition, in terms of mole ratiosof oxides, a follows: 0.9 + or - 0.2 M2/nO : Al2O3 : 5-100 SiO2 : z H2Oand M is selected from the group consisting of a mixture of alkali metalcations, especially sodium, and tetraalkylammonium cations, the alkylgroups of which preferably contain 2-5 carbon atoms.
 9. A process forthe selective separation of paraxylene from a mixture of the same withat least one other isomeric xylene which comprises contacting the samewith ZSM-8 to preferentially sorb paraxylene thereafter recovering saidparaxylene from the internal pore structure of said zeolite, said ZSM-8having the X-ray diffraction pattern as set forth in Table 4 of thespecification and a composition, in terms of mole ratios of oxides, asfollows: 0.9 + or - 0.2 M2/nO : Al2O3 : 5-100 SiO2 : z H2O wherein M isat least one cation, n is the valence thereof and z is from 0 to
 40. 10.The process of claim 8 wherein the ZSM-5 is in hydrogen form.
 11. Theprocess of claim 9 wherein the ZSM-8 is in hydrogen form.